If you (go) (a)   away, please write to me.

If he (eat) (a)   another cake, he will be sick.

I (not do)_________that if I (be)___ you.

(a)  

If you spoke louder, your classmates (understand) (a)   you.

People believe that the (a)   water has brought cancer to the local residents. (pollute)

Light pollution makes us (a)   to see the stars in the sky. (able)

Noise is considered as (a)   pollution. (environment)

Contaminants are usually (a)   to aquatic plants. (poison)

A number of cleaning products contain (a)   chemicals. (harm)

If you (find) (a)   a pen in the cellar, don't mention it to anyone.

The building is very old. He lives there. (where)

(a)  

I'll tell you something. You didn't know it before. (which)

(a)  

It was cold. However, Tom still went swimming. (Although)

(a)  

(a)   habitants have been destroyed in recent years. (nature)

I'll never forget the day. I met you then. (when)

(a)